1. Field of the Invention
The present invention relates to an organic electroluminescent device capable of emitting light by converting electric energy into light (hereinafter also referred to as “organic EL device”, “luminescent device” or “device”), in particular relates to an organic electroluminescent device excellent in light-emitting characteristics and durability.
2. Description of the Related Art
Various types of display devices using organic light-emitting materials (organic luminescent devices) are actively researched and developed these days. Above all, organic EL devices are attracting public attention as promising display devices for capable of emitting light of high luminance with low voltage.
Also in recent years, the increase in efficiency of the devices has been advanced by the use of phosphorescent materials. As phosphorescent materials, iridium complexes and platinum complexes are known. (Refer to U.S. Pat. No. 6,303,238, WO 00/57676 and WO 00/70655.)
A light-emitting layer comprising the combination of Ir(ppy) (iridium-tris(phenylpyridine)) as the dopant and CBP (4,4′-dicarbazolebiphenyl) as the host material is disclosed in patent document 3.
In WO 02/047440, an organic compound containing a deuterium atom is used, but there is no description in the same patent in connection with the effect in using the organic compound in combination with a phosphorescent metal complex material.
A carbazole material containing a deuterium atom having phosphorescence at ordinary temperature is used in JP-A-2005-48004 (The term “JP-A” as used herein refers to an “unexamined published Japanese patent application”,), but there is no description in the same patent in connection with the effect in using the material in combination with a phosphorescent metal complex material.